It is known that sometimes concentrated substances need to be preserved, usually in the form of a liquid or powder, which are dissolved in a solvent, generally composed of water, only at the time they are used.
Typically this occurs, for example, in the domestic area for advance preparation of fertilizers, herbicides or other similar solutions.
The fact that these substances can be kept in sealed containers enables the following advantages: first, a bottle or similar container can be filled with the desired solution only when there is an actual need to use it, and second, many of the substances mentioned above tend to deteriorate over time once they are put in solution, but retain their quality for extremely long periods of time if kept in an essentially airtight package.
Industrial patent no. 1,188,018 and patent application no. V192A000192 describe a container comprised of a pair of essentially hollow elements having a cylindrical shape, one of which is located inside the other, and which are assembled by mechanical engagement in correspondence with two zones of different diameter; said elements define internally, in their intermediate space, a watertight chamber in the shape of a cylindrical crown in correspondence with their reciprocal precise axial positioning.
This container is especially suitable for being fitted to the mouth of a bottle.
As claimed in the invention, the internal element can be slid in an axial direction with respect to the external element, while the latter remains fixed to the aforementioned mouth; this is easy to do while screwing down the ring nut of a sprayer capable of ejecting the solution from the bottle.
This causes the ejection of the concentrated substances from the aforementioned chamber and consequently their dropping into the bottle, causing mixing of the substances with the solvent which fills the bottle.
Thus, all the user need do is acquire the container containing the liquid which he needs, which requires an extremely small amount of space due to the high concentration of its contents, with application as a matter of general principle to any bottle, enclosure or the like.
It is also evident that given the small space occupied by a single container, it is very useful and simple for the user to acquire and keep a plurality thereof, not to mention that for the industry which produces concentrated substance it is easier to market a substance in a small container than it is to market the substance in a large bottle or the like.
However, the containers manufactured in the aforementioned other patents have the disadvantages which arise both in the phase of manufacturing the individual pieces which are to form the container itself and during use of the container, when it is applied to the bottle or the like.
Specifically, the container described in patent no. 1,188,018 is not sufficiently tight relative to the discharge of the substance from between the two aforementioned cylindrically shaped elements, due to the smallness of the surfaces which intervene in correspondence with the zone of greater diameter.
The container described in patent application no. VIA92000192, however, has a movable element provided with radial projections. This makes it complicated to manufacture using the injection molding technique, and moreover requires considerable effort to open, which takes place by widening and opening the discharge hole, not to mention the need to use a considerable amount of plastic material and the disadvantage of the volume of the aforementioned watertight chamber.